(1) Field of the Invention
The present invention pertains to a head suspension for supporting a read/write head adjacent a rotating data storage device, and in particular to a head suspension that is constructed with outriggers that enhance its lateral stiffness.
(2) Description of the Related Art
Most personal computer systems today employ direct access storage devices (DASD) or rigid disk drives for data storage. A conventional disk drive contains a spindle that is rotated by an electric motor at several thousand revolutions of the spindle per minute while the disk drive is turned on. One or more magnetically coated recording disks are mounted on the spindle for rotation therewith at axially spaced positions along the spindle.
Positioned adjacent the peripheries of the rotating disk is a head actuator column. The head actuator column typically has a plurality of actuator arms thereon, and each actuator arm supports one or more head suspensions that extend in cantilever fashion from the actuator arm to distal ends of the head suspension. The head suspensions are very precise metal springs that hold magnetic transducer read/write heads at microscopic distances above the rotating disks in the disk drive. They are typically comprised of a proximal support region that attaches the suspension to an actuator arm, a distal load region that supports the read/write head, and an intermediate spring region that biases the load region and the read/write head toward the rotating disk. The read/write heads are attached to sliders at the distal ends of each of the head suspensions. The plurality of actuator arms and their associated head suspensions support the read/write heads adjacent the top and bottom surfaces of each of the plurality of disks supported by the spindle. The read/write heads do not contact the surface of the rotating disk, but instead "fly" on the slider at a precisely maintained microscopic distance above the rotating disk surface. If this flying distance or height becomes too excessive, it can impair the ability of the read/write head to read or write data. If the flying height becomes too small causing the slider to contact the surface of the rotating disk, the resulting contact between the slider and the rotating disk can damage the surface of the disk destroying the data stored on the disk as well as potentially destroying the read/write head itself.
It is a complicated problem to design a head suspension that can cantilever a read/write head from an actuator arm at a substantially constant position relative to the surface of a rotating disk while maintaining an extremely small clearance between the head and the rotating disk surface, with the clearance sometimes being only 3 microinches. The head suspension maintains the read/write head at a correct flying distance from the surface of the rotating disk because of an equilibrium created between the upward force of the air driven under the slider by the rotation of the disk and the downward spring bias force applied by the head suspension. The suspension must also hold the head at a correct pitch angle and a correct roll angle simultaneously relative to the rotating surface of the disk. To accomplish this, the head suspension must be sufficiently flexible in the pitch and roll directions. The surface of a data storage disk is not perfectly flat. When rotating in the disk drive, the contours of the disk surface create disruptions in the air stream or air bearing created above the rotating disk surface on which the transducer head slider glides or flies. As slider sizes decrease in size, the supporting air bearing also decreases in size, decreasing the lift force exerted on the transducer head slider. Therefore, as sliders have decreased in size, the pitch and roll stiffness of suspensions has also decreased.
Head suspensions must also have a high lateral (transverse) stiffness to prevent unintended motion or sway of the suspension and its attached read/write head due to the acceleration and deceleration forces exerted on the suspension while it rapidly moves to position the read/write head at different radial locations on the disk. Even though sliders are becoming increasingly smaller and their mass is becoming smaller, the increased acceleration and deceleration forces cannot be ignored. Therefore, as head suspensions having a low pitch and roll stiffness for smaller sliders are developed, steps must be taken to avoid reducing the lateral stiffness of the head suspension while also avoided affecting the spring rate or spring bias of the head suspension spring region.